Arsenic is a known developmental toxicant and carcinogen that affects the health of tens of millions of people around the globe. Prenatal exposure to arsenic has been associated with poor birth outcomes as well as increased risk for cancer later in life. While detrimental health effects have been linked to in utero exposure to arsenic, the underlying biological mechanisms have yet to be identified. Using a Thai cohort, we recently showed that in utero exposure to arsenic results in profound genome-wide alterations in transcript levels, and these transcripts enrich for the nuclear factor-kappa beta (NF-:B) pathway. In preliminary data, we have utilized next-generation sequencing to establish that arsenicosis may be associated with altered DNA methylation patterns in CpG islands of genes of the NF-:B pathway. Taken together, these data suggest that arsenic exposure may influence both genomic and epigenomic deregulation of the NF-:B pathway. The results have piqued our interest in understanding whether in utero exposure to arsenic may result in potentially heritable epigenetic changes to DNA. Based on the preliminary findings and our interest in understanding mechanisms by which prenatal exposure to arsenic may affect health later in life, we propose this study. Here we will examine the modulation of this pathway in newborns in Gsmez Palacio, Mexico and will assess two potential contributors to this modulation, namely epigenetic alterations and genetic variation. The central hypothesis is that exposure to arsenic alters newborn expression of the NF-:B inflammatory response pathway, and that this modulation is influenced by newborn genetics and epigenetics. This research will, in a comprehensive manner, examine the effects of in utero exposure to arsenic on the signaling of the NF-:B pathway in newborns in Mexico. The proposed study leverages and promotes ongoing partnerships among researchers at the Gillings School of Global Public Health at the University of North Carolina and the University of Juarez in the State of Durango, Mexico. The investigative team includes toxicogenomicists, epidemiologists, biochemical toxicologists, clinicians and biostatisticians from both countries. The study benefits from oversight from the U.S.-Mexico Binational Center in Arizona. Data derived from this study will elucidate insights into mechanisms that associate in utero arsenic exposure with potentially long-lasting epigenetic effects that may underlie disease later in life.